1. Field of the Invention
The present invention relates to minimizing the effects of lock-in for an RLG and more particularly to dithering the optical path of the RLG by tilting the mirrors.
2. Description of the Prior Art
A ring laser gyro must overcome the problem of "lock-in" to be a practical device for measuring low rotation rates. One commaon method to minimize the effects of lock-in for an RLG is to mechanically dither the RLG. This is accomplished by using a flexure to sinusoidally rotate (dither) the RLG laser frame assembly with respect to its mounting plate. The sinusoidal motion has a large peak angular velocity but low angular displacement. The time that this input rate is below the lock-in threshold is thereby greatly reduced. The mechanical energy involved with dithering an RLG laser frame assembly presents problems when designing a system with three or more ring laser gyroscopes. Precautions must be made to avoid coupling of mechanical energy to other gyros or to the system.
One possible alternate approach is to dither the mirrors. Several patents (U.S. Pat. Nos. 4,686,683, 4,410,276, 4,410,274, 4,653,919 and 4,592,656) describe the use of mirror actuators that translate the mirror in a linear motion however none of these patents describe the improved performance technique of dithering the mirrors in an angular motion.